In the past, cutting bits for mining machines have been provided with nozzles at the forward edges thereof for spraying water onto the material being mined. Some of these bits are mounted for limited axial movement in a bore provided in a bit holder, the arrangement being such that as the bit engages and cuts into the material being mined, it will move backwardly into its bore, thereby opening a valve which admits water to the nozzles at the forward end of the bit. Such a bit is shown, for example, on page 988 of the German periodical Gluckauf 1979, No. 20. The bit shown in that publication has a cylindrical shank which reciprocates within a bore provided in a bit holder and is provided with a bore through which water is supplied to the forward end of the bit. The supply of liquid to the nozzle means at the forward end of the bit is controlled through the agency of a valve disposed in a duct which extends parallel to the cutter bit axis. When the bit is not engaging material to be mined, liquid under pressure forces it axially outwardly within the bore in which it is carried; however when the bit drives into the material being mined, the resulting axial loading on the bit forces the same back into its bore until the bit abuts the bottom of the bore, the bit shank moving the aforesaid valve into a position in which the nozzle means at the forward end of the bit communicates with a source of liquid under pressure.